/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.util.common;



import java.util.ArrayList;

import java.util.List;

import java.util.Observer;



/**

 * An abstract class used for iterables that notify observers about size in bytes of their elements,

 * as they are being iterated over.

 *

 * @param <V> the type of elements returned by this iterable

 * @param <InputT> type type of iterator returned by this iterable

 */

public abstract class ElementByteSizeObservableIterable<

        V, InputT extends ElementByteSizeObservableIterator<V>>

    implements Iterable<V> {

  private List<Observer> observers = new ArrayList<>();



  /** Derived classes override this method to return an iterator for this iterable. */

  protected abstract InputT createIterator();



  /**

   * Sets the observer, which will observe the iterator returned in the next call to iterator()

   * method. Future calls to iterator() won't be observed, unless an observer is set again.

   */

  public void addObserver(Observer observer) {

    observers.add(observer);

  }



  /**

   * Returns a new iterator for this iterable. If an observer was set in a previous call to

   * setObserver(), it will observe the iterator returned.

   */

  @Override

  public InputT iterator() {

    InputT iterator = createIterator();

    for (Observer observer : observers) {

      iterator.addObserver(observer);

    }

    observers.clear();

    return iterator;

  }

}